With summer just around the corner, I like to think of food that can be made well ahead and tastes great served cold, or at least cool, to keep me out of a hot kitchen. The vegetable part of this is usually taken care of with seasonal vegetable salads and the like. If the protein part means meat, I like to have pre-cooked pieces tucked away in the freezer.
One of my favorite cold meats is poached and marinated pork, or nibuta. (Ni means to cook in liquid, and buta is pig.) It's very easy to make, stores beautifully in the refrigerator for about a week or much longer in the freezer, and of course, tastes great - savory, slightly sweet, and very juicy. It can be sliced very thinly or julienned for one-dish meal salads or in sandwiches, or chopped up and added to stir-fries, wraps, and so on. It's a great addition to a bento box. It can be cubed or coarsely ground and used instead of char siu (roast pork) in steamed buns or bao. The possibilities are only limited by your imagination.
There's one unusual 'secret ingredient' in the poaching liquid, umeboshi or pickled plum. You can omit this if you like, but adding just one umeboshi seems to de-fat the meat a bit more than just poaching, plus making it taste a bit cleaner and fresher in an interesting way.